News Story

May 24, 2016

Environment@Harvard

The Path from Paris

0

In December 2015, more than 150 heads of state descended on Paris to attend the opening day of the 21st Conference of Parties under the United Nations Framework Convention on Climate Change (UNFCCC). When they departed, after many hope-filled speeches and handshakes, their negotiators were left to pursue an elusive goal: hash out a global agreement to put the world on a path to avoid catastrophic climate change.

After two weeks of exhausting negotiations—building on two decades of contentious talks going back to the first COP in Berlin in 1995—delegates from 195 nations emerged with a long-awaited deal. In the 12-page Paris Agreement (plus 19-page Decision), they embraced the aspirational goal of holding the global temperature rise to “well below 2 degrees C above pre-industrial levels” and to pursue efforts to limit the increase to 1.5 degrees. And for the first time ever, every participating nation committed to slowing or reducing its emissions of climate-warming pollution.

“The Paris climate talks themselves were very successful,” says Robert Stavins, the Pratt Professor of Business and Government at the Harvard Kennedy School (HKS) and Director of the Harvard Project on Climate Agreements. “They provided the foundation for a new path forward. But whether ultimately the Paris Agreement itself proves to be a success—in terms of reducing emissions at what many people consider to be a desirable rate and at reasonable cost—no one knows the answer to that…because it depends upon how the Agreement is going to be implemented in 195 countries.”

The verdicts from experts across Harvard’s various schools and disciplines struck a similar note of cautious optimism, especially in light of the significant political constraints at work in countries around the world.

“Many people who are realists—both in terms of what the science has to tell us and what the experience and theory of international agreements have to tell us—say that Paris hit a somewhat sweeter spot than we would have reasonably expected,” says William Clark, the Harvey Brooks Professor of International Science, Public Policy, and Human Develop­ment at HKS. “It is a serious step in the right direction. But, like any in­ternational environmental agreement ever, it is but one step on a pathway. We’re not there yet. Our next step could easily go backwards. Aggressive efforts to stay on track are essential.”

Critics of the deal were quick to point out the troubling gap between the ambitious rhetoric and the con­crete actions on the table: adding up all of the individual pledges at Paris still puts the world on a path toward a minimum 2.7 degrees C of warm­ing. What’s more, those pledges aren’t legally binding. Countries will face no penalties for not following through on their “intentionally nationally deter­mined contributions” (INDCs).

From this perspective, Paris looks like a collection of voluntary pledges that still fall far short of meeting the stated target. (Even 2 degrees C, some scientists say, is too risky a threshold to cross.) And many of the key de­tails—how countries will report on their progress and share information in a transparent way; how finance to assist with adaptation and mitigation will flow from developed to develop­ing countries—remain to be worked out at future negotiations.

So why all the celebration and re­newed optimism among longtime observers and participants coming out of COP21?

Stavins and others who view the Paris outcome as a success point to the structure the Agreement puts in place for potentially creating a virtuous cycle of increasing ambition among the participating parties.

In November, Stavins wrote a post on his blog outlining a “scorecard” for the upcoming talks. His checklist included five key elements: credible reporting and transparency requirements; coverage of 90 percent of global emissions; a system to finance climate adaptation and mitigation; five-year periods to return to negotiations; and putting aside unproductive disagreements regarding provisions for “loss and damage” (the politically fraught proposal to compensate poorer nations for climate impacts such as floods, droughts, and other events).

All were achieved in Paris. These provisions, Stavins and other experts say, are far more important than the aspirational global temperature targets.

“The structure of the Agreement itself provides the possibilities,” Stavins says. That structure includes a few key components designed to encourage countries to increase the ambition of their voluntary commitments over time, from a “ratcheting” mechanism to “stock-taking” periods to a “floor” for yearly finance flows. They are also designed to pressure nations into translating those commitments into meaningful actions, through a so-called “naming and shaming” process of reporting and review of emissions reductions. “If there’s adequate transparency of what emissions reductions are actually being achieved, that could provide the incentives to ratchet up commitments and actions over time.”

“There’s so much left unfinished after Paris, that’s true, but how optimistic you are is somewhat dependent on the baseline you start with,” says Jody Freeman, Cox Professor of Law and Director of Harvard Law School’s Environmental Law Program. “If your baseline is just starting with Paris, you’d say, ‘Look at all that’s left unfinished.’ If you start with the Kyoto Protocol, you’d say,

‘We’ve made tremendous progress,’ because you have the game-changer of China and India being in the process, being committed to emissions reductions.”

“For those who say this isn’t enough to get us to 2 degrees C, that’s been true of the previous 20 COPs as well,” notes Joseph Aldy, Associate Professor of Public Policy at HKS. “Everyone knows we’re taking a long path to get to whatever our climate stabilization goals will be. Let’s worry about taking the first step.”

Breaking barriers

Whether it represents the culminating step of a 21-year process, or the first step on a new path—or merely another step on humanity’s long journey—the Paris Agreement is a leap forward for a simple reason: each nation acknowledged its responsibility to reduce its share of the pollution driving climate change, and each pledged to act accordingly.

“That’s the breakthrough,” Stavins says. For the first time, every country is pushing in the same direction. “Most importantly, the INDCs submitted under the Paris Agreement account for more than 95% of global emissions, compared with the 14% coverage of the Kyoto Protocol in its current commitment period.”

“That’s the fantastic part of Paris,” agrees Aldy. “It’s the first time we have a universal effort to mitigate emissions, and universal agreement on participating and on transparency.”

This universal participation was made possible by a turn away from the approach enshrined in the KyotoProtocol, produced at COP3 in 1997. Under Kyoto’s framework, only Annex I countries (developed countries such as the United States, Canada, Australia, and most European nations) were required to reduce their carbon output, while Non-Annex I countries (most developing nations, including fast-growing economies such as China, India, and Brazil) had no obligations.

This bifurcation was founded on the principle of “common but differentiated responsibilities and respective capabilities,” recognizing the fact that the United States and other countries that industrialized early were responsible for the bulk of historical emissions. Today, China is the largest emitter of greenhouse gases, and India is the third-largest polluter. Whether it’s fair or not (a question that proved to be a sticking point at COP21, as at every past COP), for any international effort to tackle climate change to be effective, these nations must play a central role.

“The world is fundamentally different today than in 1992,” notes Aldy. “Some countries that were developing back then now have higher per capita incomes, and higher measures on the Human Development Index, than some on the bottom of Annex 1. So why can’t we expect these countries to do more? As much as we debate who is responsible, if developed country emissions go to zero tomorrow, and developing countries do nothing to change their trajectory, we’ll go way past 2 degrees C warming.” The Paris Agreement still acknowledges those “differentiated responsibilities,” but largely leaves them behind in the nuts and bolts: in the most critical components such as transparency and reporting, every country has the same obligations.

The Paris deal marks a turning point in the UNFCCC process for another reason: unlike the Kyoto Protocol, the Paris Agreement is not a legally binding treaty. Some analysts worry that Paris’ reliance on merely voluntary actions won’t be enough to generate emissions cuts that are deep and fast enough to stay under the 2-degree C threshold.

“Whether the mechanisms that were agreed upon are actually going to produce the emissions reductions that we need is a little up in the air, because there is no clear enforcement mechanism,” says James Stock, the Hitchings Burbank Professor of Political Economy. “On the other hand, having strong enforcement mechanisms is what prevented previous attempts from working. It’s the best progress that we seem to be able to make at the moment.”

But this distinction matters less than it might seem. Aldy points out that “calling commitments legally binding, and designing a penalty for noncompliance, is no more stringent or meaningful in terms of impact for promoting compliance. We can call them ‘legally binding,’ but still have countries like the United States that never ratify it, and still have countries like Canada pull out of Kyoto so it would not be found as not in compliance. At the end of the day”—even with a legally binding treaty—“it’s only peer pressure that works.”

How will we know that all of this is actually working? “The real test, over a five-year horizon, is do you start to see emissions go down?” says Stock. “This has to ramp up in a big way. (Staying under) two degrees is incredibly ambitious. Staying under 1.5 degrees would require an entirely different level of ambition, and eventually require carbon removal technologies.”

The road to Paris

The path to Paris involved a few key turning points. One was the failure of the 2009 climate talks in Copenhagen, which were widely expected to produce a binding international treaty to take force when the Kyoto Protocol expired. Instead they ended in recrimination and a watered down place-holder political accord brokered at the last minute by the U.S., China, and a group of other major economies.

In the wake of that disappointment, the new framework emerged, leaving behind the division between developed and developing countries and emphasizing a bottom-up approach, in which countries would put forward climate plans reflecting their domestic political realities and capacity to deliver.

“We saw the wall between Annex 1 and Non-Annex 1 countries start to come down in Copenhagen,” says Aldy. “You had some 40 developing countries submit goals and plans. That was never done before. We continued to see that in Durban (COP 17), where the mandate was negotiated that led to Paris, that tried to avoid this kind of split” between developed and developing countries.

“The official pivot point was the Durban Platform for Enhanced Action, which said that all countries, all parties would be under a common legal framework,” says Stavins. But he points to another event as the “real pivot point.”

“I was in Lima for the negotiations the year before Paris, and countless times I was talking with different negotiating teams, and there were difficulties in negotiations over this issue or that, but you would sense that there was a wind pushing at their backs, that kept them going—and that was the knowledge of the joint China-U.S. announcement.”

Given that the United States and China together account for almost 40 percent of global emissions, any global effort was bound to fail without their leadership. In November 2014, President Barack Obama and President Xi Jinping met in Beijing and announced a bilateral climate agreement. The United States pledged to reduce emissions by 26 percent below 2005 levels by 2025, while China promised its greenhouse gas emissions would peak by 2030, and that non-fossil sources like solar and wind would constitute 20 percent of its total energy production by 2030. These pledges would go on to form the basis of their respective INDCs at Paris.

The two leaders met again in Washington, in September 2015, to lay out the details of how they would achieve their goals. China surprised many observers by announcing the launch in 2017 of a national carbon emissions trading system covering key industrial sectors. The United States announced plans for more stringent efficiency standards for appliances and vehicles, and plans for reducing methane emissions from landfills and natural gas infrastructure. But the most significant component of the U.S. action plan was the Clean Power Plan (CPP).

The Clean Power Plan—high stakes decisions ahead

The path ahead for the U.S. to fulfill the promises it made at Paris ran into a sudden stumbling block on February 9 of this year.

On that day, the Supreme Court issued a stay of the Clean Power Plan (CPP), a rule put forward by the Obama administration to reduce emissions from power plants, which account for 40 percent of U.S. emissions.

The CPP requires states to develop plans to meet tailored targets based on their unique electricity generation profile, with the goal of reducing overall power sector emissions by 32 percent from 2005 levels by 2030. Slated to go into effect in 2022, it also puts in place incentives and regulations to get states to switch to lower-carbon electricity generation, such as wind, solar, nuclear, and natural gas.

The Court’s stay was an unprecedented move, pausing the regulation before a lower court had even heard the legal challenge from two dozen states claiming the EPA exceeded its authority under the Clean Air Act, and until the Supreme Court eventually rules on it. Many experts read the stay as a signal that the Court was likely to strike down the rule.

Then, just four days after the stay was issued, Justice Antonin Scalia died of a heart attack. A likely opponent of the plan, his passing left the Supreme Court in a likely 4-4 deadlock when it ultimately hears the case (which is expected, after the case is heard by the U.S. Court of Appeals for the D.C. Circuit court on June 2, and its ruling is likely appealed).

“If there’s a tie in the Supreme Court, the lower court ruling stands,” Stavins explains. “But it’s conceivable the Court will decide that this is a very important rule that should involve all nine justices, and therefore decide to delay a decision.” The deciding vote could then be cast by whoever eventually fills Scalia’s seat. Senate Republicans, meanwhile, are refusing to hold hearings on the nomination of Judge Merrick Garland. “So whether or not there is a CPP of the stringency envisioned in the final rule may well depend on one thing,” says Stavins, “who the next president is, because that will determine the 5-4 vote.”

In a commentary for Foreign Affairs (March 2016), Freeman noted that independent estimates suggest the CPP accounts for between 30 and 40 percent of the expected emissions reductions outlined in the U.S. INDC, making it by far the most important component of the U.S. climate plan. “In short, meeting the 2025 target is not impossible without the Clean Power Plan. But losing it would be, by any fair assessment, a blow.”

In the wake of the stay, several states have put on hold their plans to comply with the CPP. U.S. states aren’t alone in taking a “wait and see” approach to how the CPP fares in the courts—much of the world is watching what happens to U.S. climate policy, as well. The possible loss of the CPP could pose a serious credibility problem for the U.S.—one that could undermine the Paris deal.

“I received many questions about this in Paris,” Stavins says, “whether the U.S. would be able to achieve its targets and what would happen if there’s a new administration.”

“There is no question that the President’s announcement of the Clean Power Plan last October was critical to the success achieved a few weeks later in Paris,” says Richard Lazarus, the Howard and Katherine Aibel Professor of Law, and an expert on environmental law. “The Paris Agreement would not have happened without it. I expect that the Supreme Court’s stay of the Plan, pending judicial review, has raised more than a few eyebrows in the capitals of other nations, and concern as well.”

Whether that apprehension will translate to reduced ambition in those other capitals is an open question. Lazarus has conducted oral arguments in 13 cases before the Supreme Court, and has closely analyzed the Clean Power Plan. He has submitted a “friend-of-the-court” brief in the case, representing two past EPA Administrators who support the plan. “Our system of judicial review and such judicial intervention is likely so different from the way their own systems of government operate that it is hard for them to be sure of the significance (or not) of the Court’s action,” Lazarus says. “There is not yet any formal indication that the Supreme Court’s action here in the U.S. will hinder the positive momentum towards that historic result achieved in Paris. And certainly U.S. officials are working now to provide reassurance. Only time, however, will tell.”

Domestic policies critical

Stock, who served as Member of President Obama’s Council of Economic Advisors, sees the CPP as an important part of the U.S. pledge—and by extension, of the international momentum—but points to other independent economic factors that are bringing about emissions reductions domestically.

“There’s a tailwind in the form of extremely low domestic natural gas prices,” he says. “These low prices are resulting in an ever-increasing amount of substitution of natural gas for coal—that has nothing to do with the Clean Power Plan. So there’s a significant reduction just from the economics.”

He also cites other helpful tailwinds: the plunging cost of solar energy and the recent extension of the production tax credit for wind energy and the investment tax credit for solar, in the budget agreement passed in a rare moment of bipartisanship at the end of 2015. Together with the CPP, these tax credits are expected to significantly boost renewable power capacity in the coming years. “Those things together will make a great deal of difference between now and 2025.”

But Freeman points out that the CPP isn’t the only component of the U.S. climate plan plagued by uncertainty. “The pledge is based substantially on commitments that will fall to the next administration. Some policies haven’t even been adopted by agencies yet, like regulating (methane) emissions from existing oil and gas facilities. Some have been partly implemented but still could change, like the CAFE standards (for vehicle fuel economy), which are supposed to double by 2025. The EPA must conduct a mid-term evaluation of these standards by 2018 to decide whether they are still reasonable for cars planned for 2022-2025. So the question is, will they backslide or become more stringent? There is a lot of uncertainty about the policies that are the basis for our current pledge. We have to keep the foot on the pedal of executive action.”

Meanwhile, Donald Trump, the presumptive Republican nominee in the ongoing presidential primary, questions the settled science that humans are causing climate change. He has criticized U.S. participation in the Paris talks, and pledged to roll back much of President Obama’s executive actions to reduce emissions. But Stavins thinks that could be more difficult than he suspects.

“The most important element of the Paris deal is the bilateral deal between China and the U.S. And China and the U.S. have relations ongoing on a lot of things other than climate: national security, trade, monetary policy, and many other issues.” Would he really risk these other interests, he wonders, “for the sake of a symbolic statement on the Paris agreement? Not only would it be unwise, I just think (or at least hope) it’s something he wouldn’t do.”

“Most people would say that China is probably going to outperform what its INDC proclaimed, the peaking by 2030 of CO2 emissions,” says Stavins. (Indeed, there is an emerging consensus among researchers that China will peak by 2025 at the latest.) “Most people would also say, if there’s a change of political party in the White House, that would almost ensure that the U.S. will not achieve its INDC. It probably won’t anyways—it’s going to be very difficult for the U.S. to achieve it.”

Freeman sees the outcome of the U.S. presidential and congressional elections this year as likely to have a broader impact on the prospects for implementing the Paris deal than the survival of the CPP alone. There is little doubt that a Republican administration could, and likely would, put the brakes on U.S. climate action across the board, and thereby exert a major drag on the hoped-for “ratcheting” effect of Paris.

“China is highly motivated,” she says. “Their population is choking on air pollution. And the conventional pollutants causing their health problems are co-emitted with carbon dioxide, so controlling them both goes hand in hand. China also faces considerable risks from climate change, and is under pressure from the international community to join the global effort, but quite apart from both of those concerns, domestic political considerations are driving them to act.”

China has responded to U.S. policy steps with their own commitments, she says. For example, we adopted the CPP, and they announced an emissions trading program. “Can the next U.S. administration maintain that virtuous cycle?” Freeman asks. “Even if the Supreme Court upholds the CPP, if you have a president who wants to slow walk it or take it apart, that’s a real problem.”

Aldy, who, like Freeman, served as an energy and climate advisor in the Obama administration, agrees. “If our next president is opposed to taking meaningful action on climate, that obviously has a big impact on the international negotiations,” he says. “What happens with the Clean Power Plan doesn’t matter as much. President Trump is a different story.”

Transparency and trust

If the path ahead from Paris winds this year through the U.S. Circuit Court of Appeals and voting booths on Tuesday, November 8, it also winds through conference rooms in Bonn and Marrakech.

Those are the sites of upcoming meetings where delegates will continue to put flesh on the skeleton of the Paris Agreement. “That’s going to be a great deal of work,” Stavins says. Stavins and his colleagues at the Harvard Project on Climate Agreements plan to continue working to help diplomats and governments figure out how to link carbon reduction efforts such as cap-and-trade programs and carbon taxes between countries (among many other outstanding questions).

Looking beyond 2016 reveals just how contingent success will be on the acts of both individuals and institutions, on how many pieces must come together for Paris’ “ambition-ratcheting” apparatus to function as intended. In this apparent vulnerability to unpredictable events—and to the fateful decisions of individuals and institutions alike—lies both the hope and danger of the Paris deal. If conditions are right, ambition could rapidly multiply. Or it could dissipate just as quickly.

The gap between what’s required to meet the 2 degrees target and the emissions reductions in the existing pledges can only be closed by a gradual “ratcheting up” of ambition among all of the Parties. The hoped-for ratcheting of ambition depends, in turn, on the “naming and shaming” of those countries that aren’t living up to their commitments. But that peer pressure won’t materialize unless there’s a common, transparent framework for reporting and comparing countries’ actions.

In lieu of concrete mechanisms to enforce emissions reductions, the Paris accord has a process called “pledge and review.” Beginning in 2020, and every five years after that, each country will update their INDC or submit a new plan. Then, starting in 2023 and every five years after that, a “global stocktake” will take place, to review progress toward implementing the pledges.

What that looks like in practice remains to be seen. The details of how the transparency framework will function still need to be worked out. In deference to concerns from China, India, and other countries about potentially overbearing inspection regimes, the text of the agreement states that “the transparency framework shall… be implemented in a facilitative, non-intrusive, non-punitive manner, respectful of national sovereignty, and avoid placing undue burden on Parties.”

“This is going to be quite challenging going forward,” says Aldy. “A lot of work needs to be done on how to implement transparency. The hard part of ‘pledge and review’ is the review, not the pledging.”

But if the institutions can be put in place quickly and effectively, transparency can generate multiple benefits. “Transparency, shining a light on what they’re doing, and learning what works, is critical to creating confidence that countries are making good faith efforts,” says Aldy, who has closely studied best practices for transparency in other international agreements, and their relevance for monitoring climate action. “Transparency is a mechanism to raise costs both domestically and internationally for leaders who fail to deliver. Transparency can also lower the cost of agreement over time, by highlighting what is good policy practice, what works well for reducing emissions, and promoting thinking about ways to export those to other countries.”

Measuring and monitoring

Beyond the need for new institutions and protocols, the current standards for carbon emissions accounting will need to be dramatically improved—“naming and shaming” cannot work without accurate estimates of actual emissions reductions.

“If you start to think about implementing any kind of global effort to reduce carbon emissions,” says Steven Wofsy, the Rotch Professor of Atmospheric and Environmental Science “you need to know what the carbon emissions are, and where they are taking place, and what the underlying processes are.”

Wofsy argues that better measurements are needed to support the post- Paris framework. He points out that current estimates of emissions mostly come from “bottom-up” national inventories. These are developed by taking data on energy production, industrial processes, land use change, and other activities, and multiplying them by emissions rates per unit of activity. They are plagued by uncertainty, making it difficult to verify just how much pollution a given country is producing.

“They’re not very good, and not spatially disaggregated. So there’s no way to look and say, ‘Here’s where we should turn in the policy domain’,” he says. “If you think about how will we really do this, how will we develop knowledge of emissions in a way that is spatially and temporally disaggregated, it turns out that there isn’t a magic bullet. Some has to be done from space, some by making measurements in the atmosphere, some by looking much more critically at these inventories. As a scientist, my job is to help make these measurements, understand these emissions, and provide tools for people. If each of the countries of the world thinks that the world can know what they’re actually doing, that has a salutary effect on their commitments. I have observed this time and again: as soon as you begin to discuss that you have or will have the capability to measure what people are doing, that kind of clears their minds.”

Wofsy sees the role of scientists like himself as helping fuel ambition and effective action, in keeping with the collective spirit of Paris—not as helping to penalize certain players. “We’re not the carbon police. We’re the eyes and ears of the policy makers, helping them do things, not trying to put them in jail.”

Wofsy notes that some countries simply lack the technical capacity, finances, and tools to do the detailed reporting of their emissions that the Paris regime will require going forward. In others, accurately determining how much pollution they are emitting is challenging for other reasons. “For instance, China has a lot of technical capacity, but they don’t have the ability to know their emissions—that’s more of a governance issue. If we’re successful in developing methodologies that allow us to do this from space, we can circumvent these sorts of issues.”

But Wofsy is concerned that remote sensing programs to support the monitoring Paris requires aren’t advancing fast enough. “It’s not too late, but it’s not really happening right now. I don’t see a big push to do a significant step forward in remote sensing of carbon dioxide. It’s really incremental.”

Both an urgent task and a “long game”

From launching satellites to improve our understanding of what we’re doing to the climate (and who’s doing it), to putting in place institutions for shar­ing information and resources, in any scenario, implementation of the Paris Agreement will be the work of decades.

“This is part of a long process of humanity trying to come to terms with the fact it is radically restructur­ing the environment it lives in, and in turn being restructured by those changes,” Clark observes. “The com­ings and goings of one politician or another can help a little or hurt a little, but it’s the accumulation of efforts that is what gives us the direc­tion and velocity of these things.”

Freeman advises a similarly big picture perspective. “Aside from war, this is the hardest thing the world community has ever done,” says Free­man. “We’re talking about changing the global energy system in under a century. Not surprisingly, it’s incred­ibly hard.”

Meanwhile, recent temperature trends offer a sobering reminder of the challenge we’re up against. The warm­est year on record was 2015; 2016 is on track to destroy that record.

Even as the global community works to preserve a sense of urgency about bending the emissions curve down sharply, Clark emphasizes the need to keep this sense of the “long game” in mind. There will inevitably be pitfalls, wrong turns, and delays. Even in the best-case scenario, in which Paris leads to the hoped-for ratcheting of ambition among all na­tions, Clark warns that we will need to brace for hard times to come.

“Our colleague John Holdren has argued in his role as President Obama’s science advisor that the path ahead will inevitably include a mix of ‘mitigation, adaptation, and suffer­ing.’ The best we can hope for is to limit the suffering. We have enough commitment to warming of the earth system already in place that we’re go­ing to take major hits,” he says. Those least responsible for causing climate change, he adds, are going to suf­fer the most. For all of its strengths, Paris doesn’t begin to address how to allocate resources in the global “triage mode” that we will likely face, and it offers no guarantees that we will succeed. Its provisions for helping the hardest hit communities adapt to coming changes are just one of many that will require further negotiations. But Paris does increase the odds that we will tip the scales in our collective favor, toward more mitigation and adaptation and less suffering.

The next step on the long journey from Paris took place when leaders from more than 150 countries—in­cluding the U.S., China, and India— gathered at a signing ceremony at the United Nations in New York on April 22. That’s Earth Day. It was a sym­bolic gesture, of course. Emissions continued to rise that day, and will continue for many days to come.

But the solidified sense of global solidarity on display that day might, in fact, be the most important out­come of Paris. The agreement has codified the understanding that all nations—both those most respon­sible for changing our shared climate, and those least responsible but most vulnerable to the effects—must find common cause, and walk the path ahead, together.

A new sense of solidarity, a gamble on the power of peer pressure, a hope in deferred collective ambition—these may seem like shaky footing on which to base humanity’s future prospects. But looking back from the future, this breakthrough in Paris may seem a big­ger step forward on the path to main­taining a stable, livable climate than we can even realize today.

This image was originally posted to Flickr by Presidencia de la República Mexicana at https://flickr.com/photos/90642778@N05/23430273715. It was reviewed on 1 December 2015 by the FlickreviewR robot and was confirmed to be licensed under the terms of the cc-by-2.0